Process for carrying out endothermic reactions



Aug. 22,-1939.`. A. vooRHlEs, JR 2,170,437

v PROCESS FOR CARRYING OUT ENDOTHERMIC REACTIONS Filed Deo. si, 1935 l 8 ATER/AL /NLET .BOR/VER ZEAcvT/o/Y PRDQQTS Ov TAET Patented Aug. 22, 1939 UNITED STATES *Porri-:NTv OFFICE PROCESS FOR CARRYING OUT ENDOTHERMIC REACTIONS ration of Delaware Application December 31, 1935, Serial No. 56,863.

3 Claims.

The present invention relates to a method for carrying lout endothermic catalytic reactions, particularly the catalytic dehydrogenation of hydrocarbons.

It has already been proposed to employ for catalytic processes an apparatus in which a packed catalyst tube is suspended by a flange from the top of a heating chamber and depends into the chamber in which burners are arranged downwardly against the wall of the catalyst tube. The ob-ject of this construction is to avoid the difficulties attending the expansion of metal by heat at the juncture of the catalyst tube and its supporting member.

In endothermic catalytic processes in which the material to be treated is conducted through a heated packed tube or tower considerable difficulty has been encountered in obtaining a uniform distribution of heat in the interior of the tube or tower. Particularly in the catalytic dehydrogenation of hydrocarbons it has been found necessary in orderI to obtain practical yields of unsaturated hydrocarbons to apply so much heat to thevexterior of the catalytic tower, in order to attain a reaction temperature inthe central part of the tower, that considerable cracking of the hydrocarbon initial material and a consequent undesirable deposition of carbon are incurred.

Moreover, by reason of the fact that carbon deposition is favored by a large temperature differential between a hydrocarbon and a heated surface when the former is at a temperature approximating its cracking temperature, carbon deposition has -been enhanced in operation in an apparatus of the type described above by the fact that in the top of the tower there is a relatively cool zone immediately followed by a highly heated zone. This cool zone owes its existence to the fact that in order to derive the full advantages of the construction, insofar as avoidance of overheating of the juncture of the tower and its supporting member is concerned,V the burners must be spaced at an appreciable distance from this juncture. These difficulties can, in a measure, be mitigated by preheating the initial in such a manner as to direct a heating flame between the interior and the wall of the catalytic tube or tower and to also decrease thetemperature differential between the upper normally cool zone of the tower and the zone adjacent the first burner without increasing to any appreciable extent the heating of the juncture of the tower and its supporting member.

The above advantages and others which will appear from the following description are realized by constructing van apparatus forendothermic catalytic reactions in the manner shown in the accompanying drawing in which the single figure is a vertical section of a catalytic apparatus constructed in accordance with the present invention.

Referring to the drawing in detail, I is a heating chamber from the top of which is suspended a catalytic tube 2 by means of a flange 3 bolted to the top of chamber I in a suitable manner. The top and bottom of tube 2 are sealed by plates II and 5 respectively. Arranged axially of tube 2 is a passage 6 communicating at one end with the interior of chamber I and at its other end with a stack (not shown). Supported in chamber I inra suitable manner are burners 'I so arranged as to direct a flame downwardly against the walls of tube 2. The upper set of burners is spaced at a suicient distance from the top of chamber I to prevent the heating of the juncture of flange 3 and chamber I by direct heat from the flames from said burners.

An inlet 8 for initial material to be catalytically treated is provided in the plate 4. An outlet 9 for reaction products is provided in plate 5. Screens IIJ spaced from the bottom of tube 2 support a packing of catalytic material I I in said tube. For the catalytic dehydrogenation of hydrocarbons the catalytic material is usually composed of a mixture of difficultly reducible metal oxides, at least one of which is an oxide of a metal of group 6 of the periodic system.

As is apparentfrom the above description and from the drawing the hot combustion gases from the burner I instead of being led to a stack directly from chamber I are passed upwardly through the interior of the body of the catalyst. The employment of this expedient not only results in the establishment of a more uniform temperature throughout the entire catalytic body, but also provides sufficient heat in the normally cool upper portion ofthe tube 2`above the first set of burners to render more gradual the increase of the initial material from its entering temperature to the reaction temperature without seriously increasing the temperature of the juncture of ange 3 with the top of chamber I.

Obvious changes can be made in the construction described above without departing from the scope of the present invention. For example, instead of using a direct ame as a heating medium, elements 'I can supply hot combustion gases or a hot uid. Moreover the tube 2 can be immersed in a bath of molten metal. Where the annular space in tube 2 is of large area, bailies can be arranged at spaced intervals therein to cause the reaction material to follow a tortuous passage therethrough, alternately contacting the inner and outer Walls of the annular space.

The nature and objects of the present invention having been thus described, and a specific illustrative embodiment of the same having been given, what is claimed as new and useful and is desired to be secured by Letters Patent is:

1. A process for carrying out endothermic catalytic reactions which comprises passing the initial material for such reaction through an annular space packed with a suitable catalyst, passing a fluid heating medium over the exterior of said annular space in heat exchange relation therewith in a direction concurrent with the ow of reaction material therethrough and then passing said fluid heating medium through the interior of said annular space in heat exchange relation therewith in a direction counter-cur rent to the ow of reaction material therethrough.

2. A process for the catalytic dehydrogenation of a hydrocarbon which comprises passing said hydrocarbon thru an annular chamber packed with a dehydrogenation catalyst, passing a fluid heating medium over the exterior of said annular chamber in heat exchange relation therewith in a direction concurrent with the ow of reaction material therethru whereby a hot zone is established in the reaction space, and then passing said fluid heating medium thru the interior of said annular chamber in heat exchange relation therewith in a direction countercurrent to the iiow of reaction material therethrough, and maintaining indirect heat exchange relation between said countercurrent flowing heating medium and said hydrocarbon for a substantial portion of the travel of the latter before it reaches said hot zone.

3. A process for carrying out endothermic catalytic reactions which comprises passing the initial material through an annular chamber packed with a suitable catalyst, passing a uid heating medium over the exterior of said annular chamber in heat exchange relation therewithin a direction concurrent with the ow of reaction material therethrough whereby a hot zone is established in the reaction space, then passing said fluid heating medium through the interior of said annular chamber in heat exchange relation therewith in a direction countercurrent to the flow of reaction material therethrough, and maintaining indirectvheat exchange relation between said countercurrent owing heating medium and said initial material for a substantial portion of the travel of the latter before it reaches said hot zone.

ALEXIS VOORHIES, JR. 

